Wednesday, October 31, 2018

After 50 games Stockfish leads 5-2 with 43 draws.
The draw rate continues to be high at 86%, with half the superfinal over. Komodo and Stockfish both added one win, nothing is over though Stockfish has a promising lead.

Stockfish started game 41 with an eval around 1. It had a space advantage and Komodo's pieces had very little room to move. Stockfish pushed pawns on the king side, the black pieces were in no position to threaten the white king. Evals continued to climb, Stockfish's eval was around 2 at move 19.

Stockfish's king side pawns made contact with Komodo's pawns and slowly opened the king side.The white king was completely exposed yet completely safe from attacks. Komodo's pieces were helpless as Stockfish prepared its attack on the black king.

Komodo tried to exchange pieces but it was too late. The game reached a QRB vs QRN position and Stockfish grabbed two pawns.The game was adjudicated before the white passers advanced.

In game 42 Komodo was up a pawn with a central passer on move 16. Stockfish's bishop pair was very strong and evals fell to 0. In a series of exchanges Stockfish gave a rook for a bishop, the white king was exposed and all the black pieces had clear lines of attack. When the white passer advanced Stockfish ended the game with perpetual check. Another minimatch win for Stockfish.

Stockfish had an eval around 1 from the start of game 43, it was a pawn up on move 14. Evals did not change for a while, then started to increase after the queen side was blocked. The engines exchanged all rooks through an open file, Stockfish's eval was over 2. Only QB vs QB remained and there was a sudden drop in eval, apparently Komodo found a line that Stockfish overlooked. The game reduced to a queen ending, one pawn advantage was not enough for a win since Komodo had too many check attacks.

Komodo gave a pawn early in game 44, it developed its pieces faster and it forced the black king to move. Stockfish's king side rook was trapped in the corner, while Komodo's knights supported each other while staring directly at the black king.

Komodo gradually increased the pressure on the pawn on d6. Evals started to increase as Komodo doubled rooks on the d file, pinning the pawn, then added a knight and pawn to the attack. Stockfish was still a pawn ahead but evals were over 1 in favor of Komodo.

The tension was released after a series of exchanges in the center, resulting in a QRN vs QRB position with Komodo a pawn up. Komodo continued to exchange pieces reaching a N vs B ending.

Both engines agreed the pawn advantage was enough for a win, the game was adjudicated before the win was played out. Komodo wins its second minimatch.

Stockfish had an eval advantage from the start of game 45, its eval stayed under 1. Komodo had a pawn majority on the queen side, it kept the pawns safe though they were disconnected. Evals dropped to 0 in a series of exchanges that started with a Komodo knight sacrifice on the king side and ended in a BN vs R imbalance. The engines reduced to a BBN vd RB position and the game was adjudicated by the draw rule. In the reverse game 46 evals stayed low. Stockfish had a pawn majority on the queen side and Komodo created an advanced passer in the center. The game reduced to a rook ending, all the passers were captured resulting in a draw.

In game 47 Stockfish pushed pawns on the king side, exposing its king. Evals dropped to 0, Stockfish opened the king side while Komodo controlled an open file in the center. Stockfish sacrificed a bishop and forced a draw with perpetual check. In game 48 both engines castled long. Komodo had a small eval advantage for a long while, many pieces were on the board, both engines avoided exchanges. After queens and rooks were exchanged only BB vs BN remained on move 45. Evals went slowly down to 0 until adjudication.

The engines castled in opposite directions in games 49-50. Stockfish had an eval around 1 from the start of game 49. Stockfish tried to open the king side and was only partially successful, Komodo countered with a central passer. After some shuffling evals dropped to 0, a series of exchanges resulted in a RBN vs RBN position and the game was adjudicated a draw. In game 50 Komodo succeeded in opening the king side, though after the queens were exchanged the black king was not in danger. Evals were low for most of the game, the engines gradually exchanged pieces until reaching a tablebase draw.

Tuesday, October 30, 2018

After 40 games Stockfish leads 4-1 with 35 draws.
Komodo won its first game of the match. Stockfish lead is "only" 3 games, now that Komodo has proven it can beat Stockfish the games will be more exciting.

Game 31 reached a double rook ending on move 26. The engines lowered their evals to 0 and the game was adjudicated at the earliest possible moment. In game 32 Komodo opened a file on the king side and prepared to attack the black king, its own king was safe on the queen side. Komodo had an eval advantage under 1 for a while but nothing came out of king side attack, the engines started to exchange pieces and evals came down. The game reached a RB vs RN position and was adjudicated when the pawns stopped moving.

Komodo gave a knight for pawns early in game 33. At first Stockfish's eval increased but it quickly dropped back to 0. After exchanging queens Komodo was 3 pawns up, evals turned negative. Komodo pushed pawns in the center and created an advanced passer. Stockfish gave a rook for a knight so Komodo was ahead on material in a BN vs R imbalance with 3 extra pawns. Evals started to increase, the engines reduced to a RBN vs RR position, Stockfish removed the advanced black passer and Komodo pushed another passer on the king side. Komodo's eval continued to increase, though the engines seemed to be shuffling. Komodo's eval peaked close to 2 when it pushed a passer to the 3rd rank, then Stockfish exchanged a pair of rooks and captured the passer. The game reached a 7-man position, two black pawns were left. It took Komodo another 40 moves to realize it couldn't convert. A real chance for Komodo to get its first win, and in black pieces.
In game 34 Stockfish was a pawn up from the start, with a small eval advantage. The engines gradually exchanged pieces until only RRN vs RRN were left. Stockfish's eval was close to 1 and Komodo's eval was 0 when the engines started to shuffle. The game ended in a 50 move draw.

Iin game 35 Stockfish castled long and pushed pawns on the king side, its eval close to 1. Komodo gave a rook for a knight and attacked on the queen side while castling short. Stockfish opened the king side, but after exchanging queens the black king was in less danger. The game reached a RRB vs RBN position and the engines started to shuffle. After exchanging bishops the evals dropped to 0 and the game was adjudicated.

In game 36 Komodo's queen moved forward early and gave a check, Stockfish chose to move its king rather than blocking with a piece. Evals increased a little but remained under 1. Komodo's king side pawns all moved forward and it castled long.

Komodo blocked the queen side and center and slowly moved its rooks to the queen side, preparing and attack. Stockfish countered on the king side, opening a file to free the uncastled rook. Evals climbed to around 2 when the engines exchanged queens and opened the queen side.

The black pawns were weak on the queen side and Stockfish could not protect them. Komodo went up two pawns within a few moves. The engines exchanged all the rooks and only BN vs BN remained, with evals climbing fast.

A few moves later the game was adjudicated. Komodo finally wins a game, and after holding the same opening as black. Well done Komodo!

In games 37-38 white was up a knight from the start, while its king was forced to move with a protected black knight right next to it. In game 37 evals were at 0, the engines exchanged pieces but Komodo had enough left to attack the exposed white king. Stockfish pushed a pawn to the 7th rank and Komodo ended the game with a perpetual check. In game 38 both engines were reluctant to attack and the game ended in a quick repetition draw.

Stockfish started game 39 with an eval close to 1. Komodo sacrificed a knight for pawns and opened the king side, then castled long. Komodo pushed pawns on the king side and Stockfish had to protect its exposed king. Evals quickly dropped to 0, after a series of exchanges only QBN vs QR remained and Stockfish ended the game in perpetual check. In game 40 both engines castled short. Komodo held a small eval advantage for a while, evals dropped to 0 when both queens moved forward and attacked the opponent's king. Both engines decided not to risk their king and they preferred an early repetition draw.

Sunday, October 28, 2018

After 30 games Stockfish leads 4-0 with 26 draws.
The draw rate is high at 86.7%, Komodo is defending better than I expected but it still hasn't been able to find a win.

Evals were close to 0 in game 21. There were many early exchanges that left RN vs RN on move 26. The game was adjudicated by draw rule once the pawns stopped moving. In game 22 the exchanges were delayed until move 22, but then a series of exchanges resulted in a knight ending on move 32. This time the game ended in a tablebase draw.

Games 23-24 started with a Latvian opening, and in both games the engines played a line where white wins a rook for a knight. In game 23 Komodo pushed two central pawns forward, and one reached the 2nd rank protected by a bishop. Evals were at 0 despite the material difference, exposed kings and open position. The engines exchanged down to a RBN vs BBN position, the advanced pawn compensated for the material advantage and the game was adjudicated a draw. In game 24 Stockfish gave a bishop and was a full rook down, with a strong attack on the white king while Komodo's queen was far. Amazingly evals were 0 in this wild position. Komodo gave the rook back and exchanged pieces to get its king out of trouble, and then ended the game with perpetual check.

Stockfish started game 25 with an eval of 1. Komodo cleared most white pawns on the queen side and exposed the white king, the evals came down. The engines exchanged down to a QRN vs QRN position and the game ended by repetition on move 31. In game 26 Komodo had a small eval advantage from the start. Stockfish gave a rook for a knight early, the engines castled in opposite directions and both pushed pawns facing the opponent's king. The position opened up and most pieces were exchanged. The game reached a RB vs BN ending with only one black pawn. The position was a 7-man draw, it took the engines more than 50 more moves to accept the result.

There were many early exchanges in game 27, and only RRB vs RRB were left on move 26. Evals were at 0 for the rest of the game, ending in a tablebase draw. In game 28 there were again early exchanges and only RBB vs RBN remained on move 22. Komodo was hopeful for a while but the game reduced to an opposite color bishop ending. Komodo was a pawn up but not enough for more than a draw.

Stockfish started game 29 with an eval advantage under 1. It pushed pawns on the king side, creating a space advantage while leaving its king a little exposed. Most pawns remained on the board and almost all of Komodo's pieces stayed confined behind the pawns. Stockfish pushed a pawn to h6 forcing the black DS bishop to the corner almost trapped.

A few moves later the trap for the black bishop for complete. Evals gradually increased as the engines shuffled for a while and Stockfish opened the queen side. Stockfish's eval was over 4 though material was still equal, Komodo couldn't untangle itself.

Komodo gave a rook to get rid of the strong white LS bishop. The engines exchanged a few more pieces, both evals showed that Stockfish was winning.

Essentially Komodo was playing a rook down at this point, the game was adjudicated before Stockfish won more material.

In the reverse game 30 Komodo kept its king side pawns back. The engines exchanged pieces on the queen side and evals came down to 0. The game reached a BB vs BN position and was adjudicated by the draw rule.

Friday, October 26, 2018

Stockfish is slowly accumulating wins, Komodo has not been able to convert opening advantages into wins yet. I hope to see a Komodo win soon, this will make the match more interesting.

In games 9-10 black was up a knight at the book exit, the black king was exposed and the white pieces were better placed. In game 9 both engines had a 0 zero eval from start to finish. The position opened up and reached an unusual RR vs BBN imbalance. Both kings were under threat and the game ended in a perpetual check draw. Stockfish's (negative) eval jumped to 1 at the start of game 10. At first Stockfish gave the material back, though after several exchanges it was again a bishop up. Komodo used the exposed black king to win some material back, creating a R vs BN imbalance. Stockfish had a central passer that reached the 2nd rank, after exchanging queens only RR vs RBN were left and evals started to come down. Komodo gave a rook for a bishop to remove the black passer. In the R vs RN endgame Komodo was 2 pawns up, and that was enough for a draw.

Both engines stayed behind their pawn lines with very few exchanges in game 11. The position became static on move 38 and then the engines started to shuffle. The 50 move draw was avoided twice by exchanges, the game was adjudicated on move 152. In game 12 the position opened up with a series of exchanges, and the game reached a double rook ending on move 34. Komodo had an advanced passer in the center and evals were close to 1. The passer could not advance beyond the 6th rank and evals came down to 0. The game was adjudicated when all the other pawns were gone.

Komodo was up a pawn early in game 13, Stockfish was ahead in development. Komodo gave the pawn back and its defense was solid. After a series of exchanges only RRN vs RRN remained with evals at 0, the engines agreed on a draw. In game 14 Stockfish held on to its pawn advantage and Komodo had more space. After a few exchages Stockfish built a pawn line across the board and the engines started to shuffle. The game ended in a 50 move draw.

Stockfish was up a pawn early in game 15, its eval was over 1. Komodo took over the open d file with doubled rooks and attacked the white king. After a few exchanges Komodo created a central passer and evals came down to 0. Stockfish gave a rook for a knight to get rid of the passer. The engines exchanged most of the remaining pieces and the game reached a N vs R drawn ending. In game 16 the center was blocked and Komodo had a space advantage. After opening a file on the queen side the engines exchanged all the rooks, and evals came down to 0. The engines continued to exchange pieces until reaching a tablebase draw.

In game 17 Komodo traded its bishops for knights early. Stockfish's eval jumped over 1.5 when Komodo captured a pawn on the queen side, Komodo's pawns there became connected passers but they were also the black king's shield and couldn't advance. Stockfish had strong pawns in the center, and the open position also meant more strength for the white bishop pair.

The engines shuffled for a while, evals started to increase after Stockfish opened the king side. It now had two passers, one in the center and one on the king side. Komodo started to feel the danger.

After exchanging queens Stockfish captured a pawn, another exchange led to a second pawn capture. Stockfish was up 2 pawns in a RRB vs RRN position and Komodo's defense crumbled.

Stockfish reduced to a double rook ending 3 pawns up before the game was adjudicated.

In the reverse game Stockfish kept one of its bishops and castled short while Komodo castled long. Stockfish pushed pawns on the queen side and Komodo was slow in developing a king side attack. Only QRB vs QRB remained on move 29 and evals fell to 0. Komodo attacked the white king but could only get checks, the game soon ended in a draw. Another minimatch win for Stockfish.

In games 19-20 black had holes in the pawn structure on both sides of the board and no safe option for castling, while white castled long. In game 19 Komodo pushed pawns on the queen side and castled short. The queen side opened and Stockfish was busy defending against Komodo's bishop pair. Evals came down to 0, the engines exchanged pieces until QRN vs QRR remained with Stockfish 2 pawns up. The black rooks chased Stockfish's queen and the game was adjudicated a draw. In game 20 Stockfish castled long, and evals quickly fell to 0. Stockfish attacked on the queen side and for a while evals were slightly negative, but nothing came out of it. The engines exchanged pieces until reaching a drawn QR vs QR ending.

Wednesday, October 24, 2018

The TCEC cup is over, Stockfish won the event after beating Houdini in the final. Perhaps more interesting was the semi-final match against Leela (Lc0). Leela beat Ethereal and Fire in the earlier rounds in very long matches. Leela seemed to play the openings and middlegames better, but it would sometimes blunder in the endgames or be surprised by a perpetual check draw by the opponent. Leela was no match to Stockfish in season 13, it will be very interesting to see it in the next season. It will surely reach the premier division, I'm not sure whether it can handle the top 3.

The Stockfish - Komodo superfinal of season 13 has started. After 8 games Stockfish leads 2-0 with 6 draws.

Komodo opened the queen side early in game 1, and after a series of exchanges only RBN vs RNN remained on move 26. Stockfish had a queen side passer which looked dangerous, with an eval over 1.

Evals remained mostly unchaged for a while. The engines exchanged a pair of knights and Komodo used its extra pawn on the king side to create a passer in the center. Stockfish's eval started to increase after it won a pawn. It then abandoned its queen side passer and sent its rook to the king side and created passers there.

Stockfish finished the game with a rook for knight sacrifice.

The black pawn on f4 could not be saved and the 3 white passers that remained were eventually unstoppable.

In the reverse game Komodo had a pawn majority on the queen side but no passer. The pieces remained on the board longer, and evals started to drop to 0 after the engines exchanged all the rooks. The game reached a BN vs BN position on move 61. The engines continued to shuffle and exchange pieces until adjudication with only pawns left. First minimatch goes to Stockfish.

In game 3 Komodo's king remained uncastled, yet it was not in danger after the engines exchanged most pieces early. Stockfish's eval started around 1 but started to come down after 25 moves. The game ended in a repetition with RBN vs RBN on the board. Game 4 also had many early exchanges, resulting in a RBN vs RBN position. This time Komodo was a pawn up and had a 3 vs 1 pawn majority on the queen side. Komodo's eval was over 1.5 while Stockfish reduced to an opposite color bishop ending. Komodo had a queen side passer but it could not push it beyond the 6th rank. Stockfish was able to hold the white king back. It took Komodo a very long time to agree to a draw after 175 moves.

Stockfish castled long in game 5, and then it pushed the queen side pawns to force back a black bishop. This left the white king very exposed, and Komodo gave a knight while its pieces controlled the center where they could threaten the white king. Komodo thought it had enough compensation for the piece, Stockfish's eval was over 1 but it had to be careful.

The white pieces were static and pinned down, but somehow the white king remained safe. Komodo captured two pawns on the king side and created a passer in the center. Stockfish exchanged a few pieces, its king was still exposed but out of danger since only Komodo's queen could attack.

The white pieces became more active, after making sure the black passer was blocked Stockfish started to plan its attack. Komodo's king side was vulnerable and Komodo had to defend while being a piece down. Stockfish's eval was winning as it left a pawn hanging for Komodo to take.

Stockfish sacrificed a knight for the g6 pawn and pinned the rook after it took the knight. All the black pieces surrounded the king, leaving the c7 pawn unprotected. Stockfish's c pawn became an advanced passer and this was enough for a win.

In the reverse game 6 both engines castled short and the position remained closed with all pawns on the board. Komodo had a space advantage with evals over 1. Stockfish exchanged its bishops for white knights and after queens were exchanged Komodo could not find a way through the pawn wall. Komodo refused to acknowledge it was a draw, the game continued till move 197. A second minimatch win for Stockfish.

Games 7 and 8 were King's Gambit variants. There were many early exchanges in game 7 and only RB vs RN remained on move 24. Evals were low throughout the game and adjudication came quickly. Evals were low in game 8 as well. Komodo gave a knight to remove the black advancing pawns on the king side. The black king was exposed and Stockfish gave a rook for a knight to stop Komodo's attack, leading to a R vs NN imbalance. After stabilizing the queen side the engines agreed to a draw in a QR vs QNN position.

Thursday, October 4, 2018

The premier division is over, the season 13 superfinal will be between Stockfish and Komodo. Chiron and Ginkgo are relegated to division 1.There were no changes in the crosstable in the last RR, except for Chiron and Ginkgo switching places. The race for the top was over quickly, the race at the bottom of the table was still open in the final 3 rounds but Andscacs was never in real danger. Ginkgo scored its only win in the division, Houdini lost for the second time, this time against Stockfish.

Judging from the results of the last two superfinals we may assume that Stockfish is going to win again in a very one-sided match. On the other hand, the 8 games played between Stockfish and Komodo in this division had a 3-2 result, so Komodo has the ability to win games against Stockfish and it may get lucky.

The Superfinal is scheduled to start after a new TCEC cup event. I haven't decided how closely I will follow the cup event, I may take a few weeks break from the blog.

A few interesting games

Ginkgo - Andscacs: Ginkgo had an eval advantage that increased after the start, reaching over 1.5 in a RBN vs RBN position. Ginkgo had an advanced passer that got to the 7th rank, Andscacs gave a knight to stop it. Ginkgo's eval peaked over 2.5 in BN vs B ending, but Andscacs held the draw. That was Ginkgo's last realistic chance to avoid relegation. With 6 games left it is 2 points behind Andscacs.

Fire - Ethereal: The game reached a RBN vs RBN position on move 24, Fire had an eval advantage. Fire had a pawn majority on the queen side and its king advanced to the center, Ethereal had a king side passer and its king was trapped in the king side corner. It took Fire more than 20 moves to capture the black passer, with only RB vs RN left and 4 white against 3 black pawns on the queen side. After 20 more moves Fire captured another black pawn and Ethereal's defense crumbled. The game was adjudicated with 2 white passers close to queening. After this win Fire is 2.5 points ahead of Ethereal.

Houdini - Chiron: Houdini went a pawn up early in the game. It then gave a rook for a knight, evals were over 1. The engines exchanged pieces until only RB vs RR remained, Houdini created a connected pair of passers in the center and Chiron gave a rook for a bishop in an attempt to stop them. The rook ending was a win for Houdini. Double win for Houdini in this opening.

Komodo - Stockfish: Komodo had an eval advantage from the start. After a series of exchanges most of the queen side was clear, both engines had a passer. Komodo captured a pawn and created a second passer on the queen side, after exchanging queens it pushed the passer to the 7th rank. Stockfish reduced to a RB vs RB position and removed the dangerous pawn, while Komodo went two pawns up, enough for a win. The opening was biased, two white wins. Komodo is still 2 points ahead of Houdini in 2nd place.

Komodo - Ginkgo: Komodo gave a pawn early, Ginkgo's king was exposed on the king side and Komodo had an eval close to 1. Ginkgo's pawn structure had a weak e6 square, it took Komodo 15 moves to get a well guarded knight there. Ginkgo couldn't get rid of it and Komodo won a knight. The game was adjudicated in a BNN vs BN position. A double win for Komodo in this opening.

Stockfish - Houdini: See featured game below. After this loss Komodo is 3 points ahead of Houdini with 5 games remaining. Stockfish is 6 points ahead of Houdini, it has qualified to the superfinal.

Ethereal - Andscacs: Ethereal had an eval advantage, there were many early exchanges and by move 30 Ethereal was a pawn up and all the queen side pawns were gone. Evals did not move for a while in a RBN vs RBN position, but after a long shuffle Ethereal found a way to improve. Andscacs took longer to see it was losing, it became evident when Ethereal won a knight using pins and attacks on the black king. The game was adjudicated after there were no black pawns left. Andscacs is 1.5 points ahead of Chiron, still not safe.

Ginkgo - Ethereal: Ginkgo went a pawn up while its king side was a little vulnerable. Ginkgo had passers in the center and Ethereal pushed pawns on the king side. The game reached a QRR vs QRR position, evals increasing all the time. Ethereal tried to block a white passer, Ginkgo managed to get it to the 7th rank. Ethereal's defense collapsed and it started to lose pawns, the game was adjudicated with Ginkgo 3 pawns up. An unexpected win for Ginkgo, its first in the division.

Andscacs - Chiron: Andscacs was up a pawn and the game reduced to a RB vs RN position on move 23. Chiron allowed Andscacs to exchange rooks and evals jumped over 2. Chiron could not stop the white king from advancing, the game was adjudicated before Andscacs captured more pawns. Ginkgo and Chiron, switch places, Ginkgo is 7th 0.5 point ahead of Chiron.

Stockfish - Andscacs:Stockfish had an eval advantage that constantly increased. Andscacs had very little space to move, Stockfish waited for the right moment to attack and win a bishop. The game was adjudicated a few moves later.There are 3 games left for each engine. Komodo is 3 points ahead of Houdini, it will be the second qualifier for the superfinal. At the bottom the scores are Andscacs -10, Ginkgo -13, Chiron -14. The relegation race is still open.

Ginkgo - Chiron: Ginkgo had an eval advantage, temporarily it was a pawn up but the game ended in a drawn queen ending. Ginkgo and Chiron's remaining games are against much stronger engines, this was probably their last chance of a win.

Houdini - Andscacs: Houdini's eval was around 1 for a while, then started to increase as Houdini pushed pawns across the board. Andscacs attacked the king side briefly, then Houdini sacrificed a knight and created two passers on the queen side. Andscacs gave a rook to stop a passer, in a RBN vs BNN position Houdini's rook attacked the black pawns. The game was adjudicated in a N vs B ending with Houdini 2 pawns up. Despite the loss Andscacs is a point ahead of Ginkgo with one game left, Ginkgo is playing Stockfish...

Komodo - Ethereal: Komodo's eval increased to 1, Ethereal had a trapped knight on the queen side while the engines struggled to control the center. Evals jumped over 2 after Ethereal opened a way out for its knight, while Komodo created a central passer. After seeral exchanges only QR vs QBN remained, the combination of the passer and threats against the black king allowed Komodo to reduce to a winning king and pawns ending.

Stockfish had an eval of around 1 from the start, the engines castled in
opposite directions. There were several early exchanges that opened the center. Houdini gave a pawn and pushed pawns on the queen
side. Stockfish won a second pawn, clearing most of the black pawns on the queen side. However, its king faced the black major
pieces.

To get out of trouble Stockfish gave a rook for a bishop and the
game reached a QRB vs QRR position on move 26. Stockfish was two pawns up and it had 3
connected passers on the queen side, its eval continued to increase quickly. After exchanging a pair of rooks
the immediate threat to the white king was removed.

Stockfish started to push its queen side passers. Houdini's king was in the corner and under threat on the dark squares, with the white bishop on the long diagonal. By the time Houdini moved its king away from danger Stockfish formed a strong pawn chain on the queen side.

Houdini could not stop the white pawns without
losing material, the game was adjudicated a few moves later.

There were 25 games longer than 100 moves, 7 games longer than 150 moves. The
longest game was 217 moves (Komodo - Chiron, round 7,
draw).

Time per game (hours)

Median= 2:54
Average= 2:54

Openings

There
were 8-move book openings in this stage chosen by Cato. The first letter of the
ECO codes was
distributed as follows:

If we use the opening 'family name' (using format FAMILY_NAME: VARIANT....) the top 3 are:
Sicilian - 42 times
French - 18 times
King's Indian - 13 times

The
engines had almost no freedom to choose the opening variant. In fact all but one of the game pairs repeated the same ECO code and opening variant twice. The first game was a A69 Benoni and the reverse game was a E77 King's Indian.

Reverse pairs, wins

Reverse pairs, same moves Pairs of reverse games diverged very quickly, 83% of the pairs
diverged at most after 1 move. The longest repeated move sequence in a
game pair was 16 plys long (Chiron - Ginkgo, rounds 19 and 26, Philidor's defense, two draws).